10-inch Student Slide Rule with Celluloid Facings
Frederick Post model 1447D [1945]  Specimens marked "1447."
Roos model SR-105


Back: USBS Circular 47
Edges: Blank
Gutter: Table of decimal equivalents

On Roos-made rules the red ink fades easily and the celluloid facing turns very yellow.  The above scan appears whiter than the rule really is. 

 

Excerpt from 1945(?) Price List 
Second price is per dozen
 
Same as Post model 1446 (Roos 104) except that rule is painted wood with no measuring scales. 

Specimen is marked "1447" but the only listing in Post documentation is model "1447D" in 1945(?) Price List (above).  There was no 1447 or 1447D in the 1944 Price List.